Define __CHAR_BIT__

gcc defines __CHAR_BIT__ as a pre-defined macro.

Define __CHAR_BIT__ in sparse so that code that needs it (e.g. code
using CHAR_BIT from limits.h) does not generate false warnings.

Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Christopher Li <sparse@chrisli.org>
sparse: Allow override of sizeof(bool) warning

Allow an override to emit or not the sizeof(bool) warning.
Add a "-Wsizeof-bool" description to the manpage.

Signed-off-by: Joe Perches <joe@perches.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Christopher Li <sparse@chrisli.org>